Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS4034280 A
Publication typeGrant
Application numberUS 05/585,429
Publication dateJul 5, 1977
Filing dateJun 9, 1975
Priority dateJun 9, 1975
Publication number05585429, 585429, US 4034280 A, US 4034280A, US-A-4034280, US4034280 A, US4034280A
InventorsDonald L. Cronin, Bertrand F. Farber, Hartmut K. Gehm, Daniel S. Goldin
Original AssigneeTrw Inc.
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Multiple high voltage output DC-to-DC power converter
US 4034280 A
Abstract
Disclosed is a multiple output DC-to-DC converter. The DC input power is filtered and passed through a chopper preregulator. The chopper output is then passed through a current source inverter controlled by a squarewave generator. The resultant AC is passed through the primary winding of a transformer, with high voltages induced in a plurality of secondary windings. The high voltage secondary outputs are each solid-state rectified for passage to individual output loads. Multiple feedback loops control the operation of the chopper preregulator, one being responsive to the current through the primary winding and another responsive to the DC voltage level at a selected output.
Images(1)
Previous page
Next page
Claims(3)
We claim:
1. A DC to Dc power converter comprising:
(a) a transformer having a primary winding and a plurality of secondary windings;
(b) input circuit means coupled to said primary winding to cause an AC power to flow therethrough;
(c) said input circuit means including means to accept DC power at a first voltage and transistor means to convert said DC power to AC power at a first relatively low voltage for transmission through said primary winding, said transformer being such that the alternating voltage on each of said secondary windings is higher than that at said primary winding;
(d) output circuit means associated with each of said secondary windings to reconvert AC power induced in the associated secondary winding to DC power at a higher voltage;
(e) a capacitor effectively directly connected across each of said secondary windings, the capacitance of each of said capacitors being reflected across said primary winding to provide an input current source; and
(f) a peak current detector having an input coupled across said primary winding and having an output coupled across said input circuit means, thereby to protect said transistor means against over voltage due to a short in any one of said output circuits.
2. A converter as defined in claim 1 wherein said transistor means includes a transistor operated as a chopper.
3. A converter as defined in claim 2 wherein said transistor means is controlled through a feedback circuit connected between said output circuits and said transistor means.
Description

The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; 42 U.S.C. 2457).

BACKGROUND OF THE INVENTION

A. Field of Invention

This invention relates to DC-to-DC power supply converters, particularly those used in applications requiring multiple high voltage, low ripple outputs.

B. Description of Prior Art

In essence, a DC-to-DC converter is an apparatus designed to accept DC power at a first voltage and output DC power at a differing voltage. Typically, such devices operate by converting the DC input to AC, transforming the AC to a higher voltage and rectifying the higher level AC to provide the necessary DC output.

The power supply for a traveling wave tube (TWT) amplifier within an earth satellite presents special problems. Such a power supply must accept DC from a relatively low voltage power source (typically a solar array) and provide well-regulated, relatively ripple free high voltage power, in a simultaneous manner to a number of outputs having constantly varying loads.

The typical prior art DC-to-DC power converter for such an application accepts the DC source, chops it with a switching device, such as a transistor, reintegrates the signal with inductive and capacitive devices, converts the integrated DC signal to AC with a transistor inverter, transforms the AC to high voltage, rectifies the resultant to DC voltages and configures them to supply a number of outputs.

In such devices, the integration capacitance is physically located "downstream" from the chopper, between the copper inductor and the inverter. In the absence of such capacitance, the desired integration would be lacking, but the input means to the inverter would, because of the presence of the inductor, constitute a current source. The latter configuration would, therefore, limit the current drawn through the chopper and inverter transistors, even during non-steady-state conditions.

With the integration capacitance located as it is in the prior apparatus, the input means becomes a voltage source, because of the electrical energy stored in the intervening capacitor.

Accordingly, during start-up of such a converter, a large current is drawn through the chopper power switch and the inverter transistors, which can easily cause one or more to fail, unless they are highly over rated. Arcing, which can occur in TWT amplifiers, despite emphatic statements to the contrary by their manufacturers, can likewise cause current surges through all the power supply switching (chopper and inverter). Finally, because of unpredictable load variations in the TWT depressed collectors, and other factors, such conventional power supplies cannot satisfy the stringent ripple requirements imposed on TWT amplifiers in certain satellite communication system applications.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a DC-to-DC power supply for high voltage multiple output applications which can meet stringent ripple requirements, even under conditions of constantly varying output loads, with increased reliability of its power switches under start-up and other conditions of dynamic change in current drawn.

Briefly, the power supply of the present invention includes means to cause integration of its inverter input (for example, from a chopper preregulator) to be provided exclusively by an inductance-capacitance combination wherein substantially all of the capacitance is provided by means connected across the high-voltage DC outputs of the inverter. The inverter accepts the integrated DC input and converts it to AC for passage through the primary winding of a transformer. Secondary voltages are induced in each of a plurality of secondary windings, each of which is followed by rectifying means and the capacitive integrating means. The preregulator (which may consist of a transistor chopper), if included, may be governed by one or more feedback loops, which may, for example, employ means to sense peak current through the primary winding and means to sense the DC level at a selected output point.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram of an apparatus according to the preferred embodiment of the present invention.

FIG. 2 is a schematic representation of a traveling wave tube (TWT) amplifier.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 2, in a TWT amplifier, a cathode 140 is heated by a cathode heater 150, which is energized by a cathode heater supply 160. The heated cathode generates an electron "cloud" which is formed into a beam by an anode 170, energized by an anode supply 180. The beam passes through a primary coil 183 through which an input signal is passed. The input signal modulates the electron beam, which is subsequently passed through a secondary coil 185, causing current with a waveform equivalent to the modulated beam to be induced in the secondary coil. The output from the secondary coil is, in effect, an amplification of the input to the primary coil.

The beam is "collected" by a series of depressed collectors 190a-j. The sucessive collectors are maintained at a successively lower (i.e., more negative) potential, the final collector 190j being at the same potential as the cathode 140.

Because of electron beam fluctuation, the impedence represented by the various collectors constantly varies, hopefully within prescribed limits. Arcing can, however, occur. Accordingly, the current drawn by the various stages of the input 200 to the collectors can vary widely. It is necessary, therefore, to provide a power supply which can maintain low ripple and withstand such surges without failure of its switching components.

FIG. 1 shows the preferred embodiment of the present invention, which comprises a power supply satisfying these requirements. It will be noted that FIG. 1 shows only a three-stage high voltage output. It will be understood, however, than any number of stages can be provided by simply duplicating the components in any one of the stages shown.

The DC input is fist low-pass filtered by means of a passive filter 5, comprising an inductor L1 and capacitor C1. The filtered input is preregulated by being chopped by means of a switching transistor Q1, whose operation is governed by a digital control signal processor (DCSP) 30. In alternative embodiments of the present invention, a plurality of switches may be employed to provide whatever preregulation waveform is needed. In particular, a series pair of switches can be alternately activated to provide an essentially 100% duty cycle.

A series inductor L2 and flyback diode D1 cause the chopper output to be directed unidirectionally to the primary winding L3 of a transformer T. This inductor also acts as a choke to limit the current passed through it-- i.e., it causes the input and preregulation means to act together as a current source.

A series inverter consisting of a push-pull pair of transistors Q2, Q3, operated by a squarewave generator 10, causes the current in the primary winding L3 of the transformer T to alternate. This, in turn, causes AC voltages to be induced in the secondary windings L4, L5, L6 of the transformer.

The AC voltage within secondary winding L4 is rectified by a solid state rectifier 20 and passed through the integrating capacitor C2 to generate an output DC voltage whose value depends, in a conventional manner, on the input DC voltage and the ratio of windings between the secondary winding L4 and the primary winding L3 of the transformer T.

Likewise, the AC voltages induced in the other secondary windings L5 and L6 are rectified by solid state rectifiers 30 and 40, respectively, and passed through integrating capacitors C3 and C4, respectively. Each of the output stages (secondary winding, recitifier and integrator) is interconnected with its neighbor through a current limiting resistor R1, R2, respectively, which limits integrator capacitor stresses during discontinuities in output loads as well as controlling maximum energy discharged into individual outputs. In addition, the current limiting resistors prevent excessive voltage buildup in the output power return line during impedence discontinuities.

The operation of the switching transistor Q1 may be controlled by various feedback loops. In the preferred embodiment, two of these are utilized.

The first monitors the current through the primary winding L3 of the transformer T by means of a peak current detector 50, which can simply comprise a series transformer/rectifier. The DC output of the peak current detector is compared with a reference (e.g., from a zener diode) by means of a comparator 80, the output of which is passed through an operational amplifier 100.

In the second loop, the output DC level is monitored at some convenient point and compared with a reference (e.g., from a zener diode) by means of a second comparator 60, the output of which is passed through a second operational amplifier 110.

The outputs from the first operational amplifier 100 and the second operational amplifier 110 are fed to an OR-gate 120, the output of which constitutes an input to the DCSP 30 which governs the operation of the switching transistor Q1. The DCSP is conventional, and may comprise an ordinary analog-to-digital converter. The operation of the DCSP is synchronized by the squarewave generator 10.

In an alternative embodiment, the power switch Q1, and flyback diode D1 are eliminated, the inverter Q2, Q3 being utilized as the switching means. In such an embodiment, the DCSP directly operates the inverter.

Regardless of the particular embodiment, however, the position of the integration capacitance on the secondary winding (i.e., high voltage) side of the transformer T is an essential element of the present invention.

Since the capacitance means is physically absent from the inverter input means, the latter means can act as a current source. Thus, under conditions wherein the current drawn would otherwise increase dynamically, the inductor L2 in conjunction with the peak current detector loop, will serve to limit current buildup in the chopper and inverter power transistors and, therefore, prevent damage to the switching transistors.

However, even though the integration capacitance means is not physically located on the low voltage side of the transformer, and can not, therefore, cause the inverter input means to act as a voltage source (as in the prior art apparatus), its electrical effect will "reflect across" the transformer to provide te desired integration in conjunction with the inductor L2. In addition, physical placement of the integration capacitance means at the high voltage output will serve to reduce output ripple, which is a critical factor in TWT applications.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3235790 *Sep 22, 1961Feb 15, 1966Collins Corp G LMovable core transducer
US3305756 *Feb 3, 1964Feb 21, 1967Avco CorpCombined gated pulse source-transverter-rectifier power supply with sampling connection for regulation
US3657631 *Nov 25, 1970Apr 18, 1972Int Standard Electric CorpConverter circuits
US3742330 *Sep 7, 1971Jun 26, 1973Delta Electronic Control CorpCurrent mode d c to a c converters
US3889177 *Sep 24, 1973Jun 10, 1975Amp IncPower supply having substantially constant output during load switching
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4208706 *Aug 23, 1978Jun 17, 1980Sony CorporationSwitching regulator
US4236187 *Oct 12, 1978Nov 25, 1980Sharp Kabushiki KaishaPower supply voltage stabilizer
US4245288 *Oct 31, 1978Jan 13, 1981NasaElimination of current spikes in buck power converters
US4251857 *Feb 21, 1979Feb 17, 1981Sperry CorporationLoss compensation regulation for an inverter power supply
US4281373 *May 16, 1978Jul 28, 1981Societe SatelecHigh frequency voltage generator
US4293812 *Sep 26, 1979Oct 6, 1981Robert Bosch GmbhControlled d-c current supply system, with controlled current flow through a choke
US4293904 *Nov 21, 1979Oct 6, 1981The United States Of America As Represented By The Secretary Of The NavyPower frequency converter
US4344122 *Sep 5, 1980Aug 10, 1982General Electric CompanyCurrent sourced inverter with saturating output transformer
US4359679 *Jan 16, 1978Nov 16, 1982Wescom Switching, Inc.Switching d-c. regulator and load-sharing system for multiple regulators
US4581694 *Jul 5, 1984Apr 8, 1986Gte Business Communications Systems Inc.Inverter using parallel connected series pre-regulator and a synchronized switch
US4656570 *Sep 23, 1985Apr 7, 1987Pioneer Magnetics, Inc.Self-balancing push-pull square wave converter type of switched power supply
US4698742 *Aug 1, 1986Oct 6, 1987The United States Of America As Represented By The Secretary Of The Air ForceHigh-voltage milberger slip slide power conditioner
US4727463 *Jun 3, 1986Feb 23, 1988Canon Kabushiki KaishaPower supply device comprising means for modulating the output thereof
US4761728 *Jan 5, 1987Aug 2, 1988Canon Kabushiki KaishaHigh voltage generating device
US4763237 *Oct 17, 1986Aug 9, 1988Wieczorek John PDC/AC/DC Power conversion system including parallel transformers
US4821165 *Jun 15, 1987Apr 11, 1989Varian Associates, Inc.High voltage DC power supply
US4853832 *Aug 1, 1988Aug 1, 1989University Of ToledoCascaded resonant bridge converters
US4943903 *Mar 14, 1989Jul 24, 1990Cardwell Jr Gilbert IPower supply in which regulation is achieved by processing a small portion of applied power through a switching regulator
US4945464 *Sep 30, 1988Jul 31, 1990Varian Associates, Inc.High voltage DC power supply
US4956600 *Jul 1, 1988Sep 11, 1990Viteq CorporationHigh frequency current detector for a low frequency line
US4964029 *May 18, 1988Oct 16, 1990Viteq CorporationAC to DC power converter with input current waveform control for buck-boost regulation of output
US4980813 *Dec 21, 1989Dec 25, 1990Northern Telecom LimitedCurrent fed push pull power converter
US5029062 *Apr 13, 1990Jul 2, 1991Alcatel EspaceElectrical regulation and energy transfer circuit
US5111493 *Oct 31, 1990May 5, 1992Wisconsin Alumni Research FoundationPortable X-ray system with ceramic tube
US5138249 *Jun 7, 1991Aug 11, 1992Alcatel EspaceCircuit for regulating a parameter by means of a bidirectional current structure
US5317496 *Dec 18, 1990May 31, 1994Seiersen Ole SDC/DC-converter with a primary circuit and at least one secondary circuit tuned as individually oscillatory circuits
US5365419 *Mar 9, 1993Nov 15, 1994Siemens AktiengesellschaftSwitching DC converter
US5430641 *Feb 7, 1994Jul 4, 1995Dell Usa, L.P.Synchronously switching inverter and regulator
US5761057 *Jun 5, 1995Jun 2, 1998Thomson Consumer Electronics, Inc.Switched mode power supply with synchronous preconverter
US6330143Feb 23, 2000Dec 11, 2001Ford Global Technologies, Inc.Automatic over-current protection of transistors
US6504735 *Oct 5, 2001Jan 7, 200302 Micro International Ltd.Regulated voltage reducing high-voltage isolated DC/DC converter system
US6664762Jul 16, 2002Dec 16, 2003Power Designers, LlcHigh voltage battery charger
US7177164Mar 10, 2006Feb 13, 2007The United States Of America As Represented By The Administrator Of The National Aeronautics And Space AdministrationLow power, high voltage power supply with fast rise/fall time
US8223465 *Oct 28, 2009Jul 17, 2012Texas Instruments IncorporatedSurge current detection in a switch by detecting change in a duty cycle
US9071079 *Oct 17, 2011Jun 30, 2015Delta Electronics, Inc.Power supply system with multiple power sources in parallel
US20110096445 *Oct 28, 2009Apr 28, 2011Texas Instruments IncorporatedSurge Current Detection In A Switch By Detecting Change In A duty Cycle
US20120212059 *Oct 17, 2011Aug 23, 2012Chu Kuang LiuPower supply system with multiple power sources in parallel
US20150131338 *Jan 26, 2015May 14, 2015Nf CorporationPower conversion apparatus
CN101895196A *Jul 15, 2010Nov 24, 2010电子科技大学Current-mode multiplexed-output DC-DC switch power supply of secondary current sampling
CN101895196BJul 15, 2010Aug 8, 2012电子科技大学Current-mode multiplexed-output DC-DC switch power supply of secondary current sampling
DE19542357A1 *Nov 14, 1995Apr 30, 1997Abb Patent GmbhSchaltungsanordnung für einen AC/DC-Konverter mit Potentialtrennung und induktives Bauelement zur Verwendung in einer solchen Schaltungsanordnung
EP0016537A1 *Feb 20, 1980Oct 1, 1980Sperry CorporationRegulated power supply with loss compensation
Classifications
U.S. Classification363/25, 363/124, 363/97
International ClassificationH02M3/337
Cooperative ClassificationH02M3/3374, H02M2001/009
European ClassificationH02M3/337B2